Image projection systems, such as slide projectors, view-graph machines, digital projectors, and motion picture projectors are in wide use. The screens currently employed with these devices require a darkened environment. Further, the greater the amount of ambient light, the greater the light output power required to maintain the contrast at a constant value.
Typically, an image projection system includes a projector unit and a beaded screen upon which an image is projected. The light source in a conventional projector is an incandescent bulb or an arc lamp, both sources emitting an approximately black-body spectrum. The beaded screen backscatters all wavelengths toward the viewers, and does not work well in well-lighted environments because the screen also reflects the ambient light, which may diminish the clarity of the projected image.
Recently designed screens can be used in well-lighted environments if the projector light source generates three narrow-band wavelengths (red, green and blue). The screen utilizes dyes for absorbing the light spectrum between the laser or light-emitting diode (LED) emissions. Other designs use multilayer reflective stacks self-assembled photonic lattices that only reflect the laser or LED radiation. However, narrow-banded light sources (LEDs and lasers) are either low power devices or are expensive.